This invention is directed, in part, to lubricant compositions for reducing wear in internal combustion engines lubricated with a low phosphorus content lubricating oil, and to methods employing such. The lubricant compositions of this invention comprise a synergistic combination of a complex of a molybdenum/nitrogen containing compound and at least one oil-soluble, phosphorus-containing, anti-wear compound wherein the total phosphorus employed in the composition is no more than about 0.06 weight percent based on the total weight of the composition.
The following references are cited in this application as superscript numbers:
1 Buckley, III, Long Chain Aliphatic Hydrocarbyl Amine Additives Having an Oxyalkylene Hydroxy Connecting Group, U.S. Pat. No. 4,975,096, issued Dec. 4, 1990
2 Buckley, Methods and Compositions for Preventing the Precipitation of Zinc Dialkyldithiophosphates Which Contain High Percentages of a Lower Alkyl Group, U.S. Pat. No. 4,495,075, issued Jan. 22, 1985
3 Beck, et al., Impact of Oil-Derived Catalyst Poisons on FTP Performance of LEV Catalyst Systems, SAE Technical Paper 972842 (1997)
4 Johnson, et al., Effects of Oil-Derived Contaminants on Emissions from TWC-Equipped Vehicles, SAE 200-01-1881 (2000)
All of the above references are herein incorporated by reference in their entirety to the same extent as if each individual reference was specifically and individually indicated to be incorporated by reference in its entirety.
Emissions arising from automotive exhaust has been a problem for several decades and approaches for addressing this problem have included the use of unleaded fuel (to deal, in part, with lead pollution arising from leaded fuels), oxygenated fuel (to reduce hydrocarbon emissions), the use of catalytic converters (also to reduce hydrocarbon emissions), etc.
Catalytic converters are now universally employed with gasoline powered vehicles and the efficiency of these converters is directly related to the ability of the catalyst to effect conversion of unburnt or partially burnt hydrocarbons generated during combustion to carbon dioxide and water. One problem arising with the use of such converters is poisoning of the catalyst resulting in reduced catalyst efficiency. Since catalytic converters are intended for extended use, catalyst poisoning results in higher levels of atmospheric discharges of pollutants from internal combustion engines over prolonged periods of time.
In order to minimize such poisoning, the industry has set standards for both fuel and lubricant contents. For example, standards for fuels have included the use of unleaded gasoline in order to avoid lead poisoning of the catalyst1 as well as lead discharge into the environment.
As to the lubricants, one additive family currently being addressed by industry standards is the phosphorus-containing additives used in lubricant compositions employed to lubricate internal combustion engines. Specifically, phosphorus-containing additives reach the catalytic converter as a result of, for example, exhaust gas recirculation and/or oil blow-by processes as well as other methods known in the art. See, for example, Beck, et al. and Johnson, et al.3.4 In any event, the phosphorus is known to accumulate in the catalytic converter, at active metal sites; thus reducing catalyst efficiency and effectively over time, poisoning the catalyst. As a result of the above, a new focus is to lower phosphorus in the lubricating oils. For example, the draft GF-4 specifications for lubricant compositions have proposed significantly lower phosphorus contents than heretofore employed.
A problem arises when the level of phosphorus is reduced in a lubricant composition containing an oil-soluble, phosphorus-containing, anti-wear compound in that there is a significant reduction in anti-wear performance arising from this diminution in phosphorus content. One well known class of antiwear additives are metal alkylphosphates, especially zinc dialkyl dithiophosphates are generally employed in lubricating oils at phosphorous levels above 0.1 weight percent when used for wear control. At lower levels, it is not found to be an effective antiwear additive. For instance, as exemplified herein, lowering the level of phosphorus due to the presence of a metal dithiophosphate additive in a lubricant composition by one-half from 0.095 weight percent to 0.048 weight percent phosphorus results in about a seven-fold increase in engine wear.
This invention is directed to the discovery that lubricant compositions comprising a combination of a complex of a molybdenum/nitrogen-containing compound and low levels of one or more oil-soluble, phosphorus-containing, anti-wear compounds synergistically reduce wear levels when used to lubricate gasoline engines.
With regard to the above, both metal dihydrocarbyl dithiophosphates, also referred to herein as metal dithiophosphates, and molybdenum/nitrogen containing complexes, including the preferred molybdenum succinimide complexes are well known in the art. In addition, lubricant compositions comprising combinations of alkyl or alkenyl succinimides and zinc dialkyl dithiophosphate are disclosed, for example, by Buckley.2 Still further, lubricant compositions comprising both molybdenum succinimide and zinc dialkyl dithiophosphate and having a total phosphorus content of at least 0.07 weight percent based on the total weight of the composition have been hereto commercialized.
As noted above, this invention is directed, in part, to lubricant compositions comprising a combination of a complex of a molybdenum/nitrogen-containing compound and at least one oil-soluble, phosphorus-containing anti-wear compound wherein the total phosphorus employed in the composition is no more than about 0.06 weight percent based on the total weight of the composition. This combination of additives synergistically reduces wear levels when used in lubricant compositions to lubricate internal combustion engines.
Accordingly, in one of its composition aspects, this invention is directed to a lubricating oil composition comprising a major amount of an oil of lubricating viscosity,
at least one oil-soluble, phosphorus-containing, anti-wear compound wherein the weight percent of total phosphorus in the composition is no more than about 0.06 weight percent based on the total weight of the composition; and
an anti-wear effective amount of a complex of a molybdenum/nitrogen containing compound.
In a preferred embodiment, the total phosphorus in the composition is no more than 0.05 weight percent based on the total weight of the composition.
Preferably, the oil-soluble, phosphorus-containing, anti-wear compound is selected from the group consisting of metal dithiophosphates, phosphorus esters (including phosphates, phosphonates, phosphinates, phosphine oxides, phosphites, phosphonites, phosphinites, phosphines and the like), amine phosphates and amine phosphinates, sulfur-containing phosphorus esters including phosphoro monothionate and phosphoro dithionates, phosphoramides, phosphonamides and the like. More preferably, the phosphorus-containing compound is a metal dithiophosphate and, even more preferably, a zinc dithiophosphate.
The complex of a molybdenum/nitrogen-containing compound is preferably a molybdenum succinimide. The complex includes both sulfurized and non-sulfurized forms and, preferably, the complex is sulfurized.
A particularly preferred complex of a molybdenum/nitrogen containing compound is disclosed in commonly assigned U.S. Ser. No. 10/159,446 filed on May 31, 2002 as and entitled xe2x80x9cReduced Color Molybdenum-Containing Composition and a Method of Making Samexe2x80x9d which application is incorporated herein by reference in its entirety.
In one of its method aspects, this invention is directed to a method for controlling wear during operation of an internal combustion engine, which method comprises operating the engine with a lubricant composition comprising a major amount of an oil of lubricating viscosity, at least one oil-soluble, phosphorus-containing, anti-wear compound wherein the weight percent of total phosphorus in the composition is no more than about 0.06 weight percent based on the total weight of the composition, and an anti-wear effective amount of a molybdenum/nitrogen-containing compound.
This invention is directed, in part, to novel lubricant compositions comprising a combination of a molybdenum/nitrogen-containing compound and at least one phosphorus-containing compound wherein the total phosphorus employed in the composition is no more than about 0.06 weight percent based on the total weight of the composition.
Each of these components in the claimed composition will be described in detail herein. However, prior to such a description, the following terms will first be defined.
The term xe2x80x9can oil-soluble, phosphorus-containing, anti-wear compoundxe2x80x9d refers to additives in lubricant compositions that contain phosphorus and which exhibit an anti-wear benefit, either alone or when used in combination with other additives, during operation of an internal combustion engine that is lubricated with such a lubricant composition. The phosphorus in such additives is typically integral to the additive function.
The term xe2x80x9ctotal phosphorusxe2x80x9d refers to the total amount of phosphorus in the lubricant composition regardless of whether such phosphorus is present as part of an oil-soluble, phosphorus-containing, anti-wear compound or in the form of a contaminant in the lubricant composition such as residual phosphorus remaining due to the presence of P2S5 used to prepare metal dihydrocarbyl dithiophosphates. In either event, the amount of phosphorus permitted in the lubricant composition is independent of source. Preferably, however, the phosphorus is part of a lubricant additive.
The molybdenum/nitrogen-containing complexes (additives) employed in the compositions and methods of this invention are well known in the art and are complexes of molybdic acid and an oil-soluble basic nitrogen-containing compound. Such additives have been used as lubricating oil additives to control oxidation and wear of engine components. Since their discovery, such complexes have been widely used as engine lubricating oil additives in automotive crankcase oils.
The molybdenum/nitrogen-containing complex is normally made with an organic solvent comprising a polar promoter during a complexation step and procedures for preparing such complexes are described, for example, in U.S. Pat. Nos. 4,402,840; 4,394,279; 4,370,246; 4,369,119; 4,285,822; 4,283,295; 4,265,773; 4,263,152; 4,261,843; 4,259,1951 and 4,259,194 all of which are incorporated herein by reference in their entirety. As shown in these references, the molybdenum/nitrogen-containing complex can further be sulfurized.
The polar promoter used in the preparation of the molybdenum or molybdenum/sulfur compositions of this invention is one that facilitates the interaction between the molybdenum compound and the basic nitrogen compound. A wide variety of such promoters are well known to those skilled in the art. Typical promoters are 1,3-propanediol, 1,4-butane-diol, diethylene glycol, butyl cellosolve, propylene glycol, 1,4-butyleneglycol, methyl carbitol, ethanolamine, diethanolamine, N-methyl-diethanol-amine, dimethyl formamide, N-methyl acetamide, dimethyl acetamide, methanol, ethylene glycol, dimethyl sulfoxide, hexamethyl phosphoramide, tetrahydrofuran and water. Preferred are water and ethylene glycol. Particularly preferred is water.
While ordinarily the polar promoter is separately added to the reaction mixture, it may also be present, particularly in the case of water, as a component of non-anhydrous starting materials or as waters of hydration in the acidic molybdenum compound, such as (NH4)6Mo7O24.4H2O. Water may also be added as ammonium hydroxide.
The complexation step can be followed by a sulfurization step as disclosed in King et al., U.S. Pat. No. 4,263,152, which is herein incorporated by reference. Related King et al., U.S. Pat. No. 4,272,387, is also incorporated by reference.
Representative sulfur sources for preparing the sulfurized complexes described herein are sulfur, hydrogen sulfide, sulfur monochloride, sulfur dichloride, phosphorus pentasulfide, R2Sx where R is hydrocarbyl, preferably C1-40 alkyl, and x is at least 2, inorganic sulfides and polysulfides such as (NH4)2Sx, where x is at least 1, thioacetamide, thiourea, and mercaptans of the formula RSH where R is as defined above. Also useful as sulfurizing agents are traditional sulfur-containing antioxidants such as wax sulfides and polysulfides, sulfurized olefins, sulfurized carboxylic and esters and sulfurized ester-olefins, and sulfurized alkylphenols and the metal salts thereof.
The sulfurized fatty acid esters are prepared by reacting sulfur, sulfur monochloride, and/or sulfur dichloride with an unsaturated fatty ester under elevated temperatures. Typical esters include C1-C20 alkyl esters of C8-C24 unsaturated fatty acids, such as palmitoleic, oleic, ricinoleic, petroselinic, vaccenic, linoleic, linolenic, oleostearic, licanic, paranaric, tariric, gadoleic, arachidonic, cetoleic, etc. Particularly good results have been obtained with mixed unsaturated fatty acid esters, such as are obtained from animal fats and vegetable oils, such as tall oil, linseed oil, olive oil, castor oil, peanut oil, rape oil, fish oil, sperm oil, and so forth.
Exemplary fatty esters include lauryl tallate, methyl oleate, ethyl oleate, lauryl oleate, cetyl oleate, cetyl linoleate, lauryl ricinoleate, oleyl linoleate, oleyl stearate, and alkyl glycerides.
Cross-sulfurized ester olefins, such as a sulfurized mixture of C10-C25 olefins with fatty acid esters of C10-C25 fatty acids and C1-C25 alkyl or alkenyl alcohols, wherein the fatty acid and/or the alcohol is unsaturated may also be used.
Sulfurized olefins are prepared by the reaction of the C3-C6 olefin or a low-molecular-weight polyolefin derived therefrom with a sulfur-containing compound such as sulfur, sulfur monochloride, and/or sulfur dichloride.
Also useful are the aromatic and alkyl sulfides, such as dibenzyl sulfide, dixylyl sulfide, dicetyl sulfide, diparaffin wax sulfide and polysulfide, cracked wax-olefin sulfides and so forth. They can be prepared by treating the starting material, e.g., olefinically unsaturated compounds, with sulfur, sulfur monochloride, and sulfur dichloride. Particularly preferred are the paraffin wax thiomers described in U.S. Pat. No. 2,346,156.
Sulfurized alkyl phenols and the metal salts thereof include compounds such as sulfirized dodecylphenol and the calcium salts thereof. The alkyl group ordinarily contains from 9-300 carbon atoms. The metal salt may be preferably, a Group I or Group II salt, especially sodium, calcium, magnesium, or barium.
Preferred sulfur sources are sulfur, hydrogen sulfide, phosphorus pentasulfide, R2Sx where R is hydrocarbyl, preferably C1-C10 alkyl, and x is at least 3, mercaptans wherein R is C1-C10 alkyl, inorganic sulfides and polysulfides, thioacetamide, and thiourea. Most preferred sulfur sources are sulfur, hydrogen sulfide, phosphorus pentasulfide, and inorganic sulfides and polysulfides.
The molybdenum compounds used to prepare the molybdenum complexes used in the compositions of this invention are acidic molybdenum compounds or salts of acidic molybdenum compounds. By acidic is meant that the molybdenum compounds will react with a basic nitrogen atom of, e.g., an alkenyl succinimide in which the basicity of the basic nitrogen compound can be determined by ASTM test D664 or the D2896 titration procedure. Typically, these molybdenum compounds are hexavalent and are represented by the following compositions: molybdic oxide, molybdic acid, ammonium molybdate, sodium molybdate, potassium molybdates and other alkaline metal molybdates and other molybdenum salts such as hydrogen salts, e.g., hydrogen sodium molybdate, MoOCl4, MoO2Br2, Mo2O3Cl6, molybdenum trioxide or similar acidic molybdenum compounds. Preferred acidic molybdenum compounds are molybdic oxide, molybdic acid, ammonium molybdate, and alkali metal molybdates. Particularly preferred is molybdic oxide.
In a particularly preferred embodiment, low color intensity molybdenum/nitrogen-containing complexes used in this invention are prepared from a mixture of the molybdenum compound and a polar promoter with a basic nitrogen-containing compound, e.g., an alkenyl succinimide, with or without diluent. The diluent is used, if necessary, to provide a suitable viscosity for easy stirring. Typical diluents are lubricating oil and liquid compounds containing only carbon and hydrogen. If desired, ammonium hydroxide may also be added to the reaction mixture to provide a solution of ammonium molybdate. In this reaction, a basic nitrogen-containing compound, neutral oil, and water are charged to the reactor. The reactor is agitated and heated at a temperature less than or equal to about 120xc2x0 C., preferably from about 70xc2x0 C. to about 90xc2x0 C. Molybdic oxide is then charged to the reactor and the temperature is maintained at a temperature less than or equal to about 120xc2x0 C., preferably at about 70xc2x0 C. to about 90xc2x0 C., until the molybdenum is sufficiently reacted. The reaction time for this step is typically in the range of from about 2 to about 30 hours and preferably from about 2 to about 10 hours.
Typically excess water is removed from the reaction mixture. Removal methods include but are not limited to vacuum distillation or nitrogen stripping while preferably maintaining the temperature of the reactor at a temperature less than or equal to about 120xc2x0 C. and more preferably between about 70xc2x0 C. to about 90xc2x0 C. The temperature during the stripping process is preferably held at a temperature less than or equal to about 120xc2x0 C. to maintain the low color intensity of the molybdenum-containing composition. However, darker molybdenum/nitrogen-containing compositions are likewise useful in this invention. Stripping is ordinarily carried out under reduced pressure. The pressure may be reduced incrementally to avoid problems with foaming. After the desired pressure is reached, the stripping step is typically carried out for a period of about 0.5 to about 5 hours and preferably from about 0.5 to about 2 hours.
Optionally, the reaction mixture may be further reacted with a sulfur source as defined above, at a suitable pressure and temperature that preferably does not exceed 120xc2x0 C. The sulfurization step is typically carried out for a period of from about 0.5 to about 5 hours and preferably from about 0.5 to about 2 hours. In some cases, removal of the polar promoter from the reaction mixture may be desirable prior to completion of reaction with the sulfur source.
In the reaction mixture, the ratio of molybdenum compound to basic nitrogen-containing compound is not critical; however, as the amount of molybdenum with respect to basic nitrogen increases, the filtration of the product becomes more difficult. Since the molybdenum component probably oligomerizes, it is advantageous to add as much molybdenum as can easily be maintained in the composition. Usually, the reaction mixture will have charged to it from 0.01 to 2.00 atoms of molybdenum per basic nitrogen atom. Preferably from 0.4 to 1.0, and most preferably from 0.4 to 0.7, atoms of molybdenum per atom of basic nitrogen is added to the reaction mixture.
When employed, the sulfur source is usually charged to the reaction mixture in such a ratio to provide up to 1 atom of sulfur per atom of molybdenum. A preferred ratio is 0.1 atom of sulfur per atom of molybdenum.
The polar promoter, which is preferably water, is ordinarily present in the ratio of 0.5 to 25 moles of promoter per mole of molybdenum. Preferably from 1.0 to 4 moles of the promoter is present per mole of molybdenum.
The basic nitrogen containing compound used to prepare the molybdenum complexes described herein are disclosed in numerous references and are well known in the art. The basic nitrogen compound used to prepare the molybdenum/sulfur compositions must contain basic nitrogen as measured by ASTM D664 test or D2896. It is preferably oil-soluble. The basic nitrogen compound is selected from the group consisting of succinimides, carboxylic acid amides, hydrocarbyl monoamines, hydrocarbon polyamines, Mannich bases, phosphoramides, thiophosphoramides, phosphonamides, dispersant viscosity index improvers, and mixtures thereof. These basic nitrogen-containing compounds are described below (keeping in mind the reservation that each must have at least one basic nitrogen). Any of the nitrogen-containing compositions may be post-treated with, e.g., boron, using procedures well known in the art so long as the compositions continue to contain basic nitrogen. These post-treatments are particularly applicable to succinimides and Mannich base compositions.
The succinimides and polysuccinimides that can be used to prepare the molybdenum/nitrogen-containing complexes described herein are disclosed in numerous references and are well known in the art. Certain fundamental types of succinimides and the related materials encompassed by the term of art xe2x80x9csuccinimidexe2x80x9d are taught in U.S. Pat. Nos. 3,219,666; 3,172,892; and 3,272,746, the disclosures of which are hereby incorporated by reference. The term xe2x80x9csuccinimidexe2x80x9d is understood in the art to include many of the amide, imide, and amidine species which may also be formed. The predominant product, however, is a succinimide and this term has been generally accepted as meaning the product of a reaction of an alkenyl substituted succinic acid or anhydride with a nitrogen-containing compound. Preferred succinimides, because of their commercial availability, are those succinimides prepared from a hydrocarbyl succinic anhydride, wherein the hydrocarbyl group contains from about 24 to about 350 carbon atoms, and an ethylene amine, said ethylene amines being especially characterized by ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, and higher molecular weight polyethylene amines. Particularly preferred are those succinimides prepared from polyisobutenyl succinic anhydride of 70 to 128 carbon atoms and tetraethylene pentamine or higher molecular weight polyethylene amines or mixtures of polyethylene amines such that the average molecular weight of the mixture is about 205 Daltons thereof.
Also included within the term xe2x80x9csuccinimidexe2x80x9d are the cooligomers of a hydrocarbyl succinic acid or anhydride and a polysecondary amine containing at least one tertiary amino nitrogen in addition to two or more secondary amino groups. Ordinarily, this composition has between 1,500 and 50,000 average molecular weight. A typical compound would be that prepared by reacting polyisobutenyl succinic anhydride and ethylene dipiperazine.
Carboxylic acid amide compounds are also suitable starting materials for preparing the molybdenum or molybdenum/nitrogen-containing complexes used in this invention. Typical of such compounds are those disclosed in U.S. Pat. No. 3,405,064, the disclosure of which is hereby incorporated by reference. These compounds are ordinarily prepared by reacting a carboxylic acid or anhydride or ester thereof, having at least 12 to about 350 aliphatic carbon atoms in the principal aliphatic chain and, if desired, having sufficient pendant aliphatic groups to render the molecule oil soluble with an amine or a hydrocarbyl polyamine, such as an ethylene amine, to give a mono or polycarboxylic acid amide. Preferred are those amides prepared from (1) a carboxylic acid of the formula R2COOH, where R2 is C12-20 alkyl or a mixture of this acid with a polyisobutenyl carboxylic acid in which the polyisobutenyl group contains from 72 to 128 carbon atoms and (2) an ethylene amine, especially triethylene tetramine or tetraethylene pentamine or mixtures thereof.
Another class of compounds that are useful in this invention are hydrocarbyl monoamines and hydrocarbyl polyamines, preferably of the type disclosed in U.S. Pat. No. 3,574,576, the disclosure of which is hereby incorporated by reference. The hydrocarbyl group, which is preferably alkyl, or olefinic having one or two sites of unsaturation, usually contains from 9 to 350, preferably from 20 to 200 carbon atoms. Particularly preferred hydrocarbyl polyamines are those which are derived, e.g., by reacting polyisobutenyl chloride and a polyalkylene polyamine, such as an ethylene amine, e.g., ethylene diamine, diethylene triamine, tetraethylene pentamine, 2-aminoethylpiperazine, 1,3-propylene diamine, 1,2-propylenediamine, and the like.
Another class of compounds useful for supplying basic nitrogen is the class of Mannich base compounds. These compounds are prepared from a phenol or C9-200 alkylphenol, an aldehyde, such as formaldehyde or formaldehyde precursor such as paraformaldehyde, and an amine compound. The amine may be a mono or polyamine and typical compounds are prepared from an alkylamine, such as methylamine or an ethylene amine, such as, diethylene triamine, or tetraethylene pentamine, and the like. The phenolic material may be sulfurized and preferably is dodecylphenol or a C80-100 alkylphenol. Typical Mannich bases that can be used in this invention are disclosed in U.S. Pat. Nos. 4,157,309 and 3,649,229; 3,368,972; and 3,539,663, the disclosures of which are hereby incorporated by reference. The last referenced patent discloses Mannich bases prepared by reacting an alkylphenol having at least 50 carbon atoms, preferably 50 to 200 carbon atoms with formaldehyde and an alkylene polyamine HN(ANH)nH where A is a saturated divalent alkyl hydrocarbon of 2 to 6 carbon atoms and n is 1-10 and where the condensation product of said alkylene polyamine may be further reacted with urea or thiourea. The utility of these Mannich bases as starting materials for preparing lubricating oil additives can often be significantly improved by treating the Mannich base using conventional techniques to introduce boron into the compound.
Another class of compounds useful for preparing the molybdenum/nitrogen-containing complexes including sulfurized versions thereof for use in this invention is the class of phosphoramides and phosphonamides such as those disclosed in U.S. Pat. Nos. 3,909,430 and 3,968,157, the disclosures of which are hereby incorporated by reference. These compounds may be prepared by forming a phosphorus compound having at least one P-N bond. They can be prepared, for example, by reacting phosphorus oxychloride with a hydrocarbyl diol in the presence of a monoamine or by reacting phosphorus oxychloride with a difunctional secondary amine and a mono-functional amine. Thiophosphoro amides can be prepared by reacting an unsaturated hydrocarbon compound containing from 2 to 450 or more carbon atoms, such as polyethylene, polyisobutylene, polypropylene, ethylene, 1-hexene, 1,3-hexadiene, isobutylene, 4-methyl-1-pentene, and the like, with phosphorus pentasulfide and a nitrogen-containing compound as defined above, particularly an alkylamine, alkyldiamine, alkylpolyamine, or an alkyleneamine, such as ethylene diamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and the like.
Another class of nitrogen-containing compounds useful in preparing molybdenum/nitrogen-containing complexes including sulfurized versions thereof for use in this invention includes the so-called dispersant viscosity index improvers (VI improvers). These VI improvers are commonly prepared by functionalizing a hydrocarbon polymer, especially a polymer derived from ethylene and/or propylene, optionally containing additional units derived from one or more co-monomers such as alicyclic or aliphatic olefins or diolefins. The functionalization may be carried out by a variety of processes that introduce a reactive site or sites that usually has at least one oxygen atom on the polymer. The polymer is then contacted with a nitrogen-containing source to introduce nitrogen-containing functional groups on the polymer backbone. Commonly used nitrogen sources include any basic nitrogen compound especially those nitrogen-containing compounds and compositions described herein. Preferred nitrogen sources are alkylene amines, such as ethylene amines, alkyl amines, and Mannich bases.
Preferred basic nitrogen compounds for use in this invention are succinimides, carboxylic acid amides, and Mannich bases. The preferred succinimide is prepared from a polyalkylene amine or mixtures thereof reacted with a polyisobutenyl succinic anhydride derived from the reaction of polyisobutylene with maleic anhydride as described in Harrison, et al., U.S. Pat. No. 6,156,850.
The following examples illustrate procedures for the synthesis of preferred low color intensity molybdenum/nitrogen-containing complexes followed by the darker, high color intensity molybdenum/nitrogen-containing complexes, both used in the compositions and methods of this invention.